Many types of concrete structures, such as concrete slabs or floors, include reinforcement bars which are used to increase the strength and integrity of the concrete structure. The reinforcement bars are typically arranged in rows or grids within a form into which concrete is poured and allowed to cure or harden. Spacers or chairs are conventionally used to support and hold in position the reinforcement bars a desired distance above the bottom of the concrete form. The spacers or chairs allow the reinforcement bars to be fully encased by the concrete and positioned at a predetermined depth within the concrete structure.
Conventional chairs or spacers are constructed at several different standard heights because reinforcement bars are frequently spaced at different heights according to the type of structure to be formed. One drawback to using rigid chairs of a predetermined height is that if one or more reinforcement bars are to be supported at different heights multiple different chairs must be used. This requires a contractor to predetermine how many chairs of a particular height are necessary and bring the necessary number of chairs of that particular height to the site where the concrete will be formed. Different numbers of chairs of different heights must be brought to the job site. The contractor may miscalculate the number of chairs of select heights, thereby causing unnecessary delay and expense. Additionally, if too many chairs are erroneously brought to the job site, excess chairs must be removed from the job site once the job is completed, again causing unnecessary time and expense.
One type of reinforcement bar used in horizontally oriented concrete structures or slabs is called a post-tension cable. Post-tension cables are used to put concrete structures in compression. Post-tension cables are held in a drooped or arched shaped with chairs of different heights. The ends of the post-tension cable are held up by the concrete form prior to the pouring of the concrete. Once the concrete has been poured and allowed to harden or cure in the form, the ends of the post-tension cable are pulled in opposite directions, so the post-tension cable is placed in tension. The tension placed on the post-tension cable thereby puts the concrete section in compression. The location of the post-tension cable in a drooping orientation in the cured concrete creates a lifting force on the center of the concrete section or span once the post-tension cable is put in tension.
In order to hold the post-tension cable in a drooping orientation before the concrete is poured and allowed to harden, multiple support chairs of varying heights are required to be placed underneath the post-tension cable at predetermined locations along the length of the post-tension cable. This requires the contractor or builder to predetermine which support chairs to purchase for each job and how many of each type to order from the distributor. The distributor must then correctly count out and transport the correct number of each desired chair to the job site. Placement personnel must then place the correct support chair in the correct location before the concrete is poured. Each step in this process is subject to human or computer error. Each error may require additional time and money to correct, thus adding additional costs to the job and potentially delaying the pouring of the concrete.
There is thus a need for a support chair which is able to support a predetermined gauge of reinforcement cable at multiple heights. A contractor could then order multiple support chairs based only on the gauge of reinforcement cable being used without having to worry about how many chairs of a predetermined height are required for a particular job. The distributor would not need to count out and package the support chairs by height. Lastly, placement personnel would be able to pick up and place the support chairs in a predetermined location before placing the post-tension cable in an appropriate receptacle or slot at the appropriate height.